1. Field of the Invention
The present invention relates to a semiconductor pressure sensor including a resistive element formed at a diaphragm, wiring arranged on an insulating film that covers the resistive element and the diaphragm, and a via that is arranged at the insulating film and electrically connects the resistive element and the wiring. The present invention also relates to a method of fabricating such a semiconductor pressure sensor.
2. Description of the Related Art
FIG. 1 is a cross-sectional view of a conventional semiconductor pressure sensor. The illustrated semiconductor pressure sensor 100 of FIG. 1 includes a wiring region J in which wiring 112 is formed and wiring region K in which wiring 113 is formed.
As is shown in FIG. 1, the semiconductor pressure sensor 100 includes a diaphragm 101, a diaphragm supporting element 102, a first resistive element 104, a second resistive element 105, an insulating film 107, vias 108 and 109, wirings 112 and 113, and a protective film 115.
The diaphragm 101 is arranged into a thin film so that it may be deformed when external pressure is applied thereto. The diaphragm supporting element 102 has a frame structure and is arranged around the periphery of the diaphragm 101. The diaphragm supporting element 102 is arranged to be thicker than the diaphragm 101 and is configured to support the diaphragm 101. The diaphragm 101 and the diaphragm supporting element 102 may be created from a silicon substrate, for example.
The first and second resistive elements 104 and 105 are arranged on the upper face 101A of the diaphragm 101. The first resistive element 104 is a reference resistive element that is arranged at approximately the center of the diaphragm 101. The second resistive element 105 is arranged at the periphery of the diaphragm 101.
The insulating film 107 is arranged to cover the upper face 100A of the diaphragm 101 and portions of the upper face of the first and second resistive elements 104 and 105. The upper face 107A of the insulating film 107 is arranged into a flat surface. The insulating film 107 has a through hole 117 exposing the upper face of the first resistive element 104 and a through hole 118 exposing the upper face of the second resistive element 105.
The via 108 is arranged within the through hole 117. The lower end portion of the via 108 is arranged to be in contact with the first resistive element 104. The via 109 is arranged within the through hole 118. The lower end portion of the via 109 is arranged to be in contact with the second resistive element 105.
The wiring 112 is arranged on a portion of the upper face 107A of the insulating film 107 corresponding to the location where the via 108 is formed (i.e., wiring region J). The lower face of the wiring 112 is arranged to be in contact with the upper end portion of the via 108. In this way, the wiring 112 may be electrically connected to the first resistive element 104 through the via 108.
The wiring 113 is arranged on a portion of the upper face 107A of the insulating film 107 corresponding to the location where the via 109 is formed (i.e., wiring region K). The lower face of the wiring 113 is arranged to be in contact with the upper end portion of the via 109. In this way, the wiring 113 may be electrically connected to the second resistive element 105 through the via 109.
The protective film 115 is arranged to cover the wirings 112, 113, and the upper face 107A of the insulating film 107. The protective film 115 is for protecting the wirings 112 and 113.
When pressure is applied to the diaphragm 101 and the diaphragm 101 is deformed as a result, the semiconductor pressure sensor 100 having the above-described configuration may detect the pressure applied to the diaphragm 101 based on the difference in the resistance values of the first and second resistive elements 104 and 105 (e.g., see Japanese Laid-Open Patent Publication No. 6-140640).
However, in the above-described conventional semiconductor pressure sensor 100, the wirings 112 and 113 are formed on the upper face 107A of the insulating film 107 which is arranged into a flat surface so that a difference is created in the thickness of the structures formed on portions of the diaphragm 101 corresponding to the wiring regions J and K (i.e., structure including the insulating film 107, the via 108 or 109, and the wiring 112 or 113) and the thickness of the structures arranged on portions of the diaphragm 101 surrounding the wiring regions J and K (i.e., insulating film 107). As a consequence, a difference is created in the amount of deformation occurring at the portions of the diaphragm 101 corresponding to the wiring regions J and K and the amount of deformation occurring at the portions of the diaphragm 101 surrounding the wiring regions J and K so that detection accuracy for detecting the pressure applied to the diaphragm 101 may be degraded.